Officials had concerns about the increasing number of injuries on a Long Island Rail Road tunnel construction before a chunk of falling concrete killed a sandhog.

Sandhogs are urban miners who brave the dark, damp conditions far beneath New York City to build tunnels for sewer, water and transportation. Historically, tunnel excavation and construction has been a dangerous job for sandhogs. In recent years, advances in machinery and regulatory oversight have made the job safer.

120 feet below Manhattan on Thursday night, 26-year-old sandhog Michael O’Brien died as he worked on the Metropolitan Transit Authority’s East Side Access project that will connect the Long Island Rail Road's (LIRR) Main and Port Washington lines in Queens to a new LIRR terminal beneath Grand Central Terminal in Manhattan.

According to The New York Times, a piece of sprayed-on concrete from the ceiling of the tunnel broke off, falling and striking O’Brien as he worked below.

On the job only three weeks, O’Brien was a member of the NYC Sandhogs Local 147 and worked alongside his father in the tunnel. His father Robert O’Brien stood just feet away when the accident occurred and afterwards performed CPR in a desperate attempt to save his son, reports The New York Daily News.

Before O’Brien’s death, officials in the MTA were concerned about the rise of worker injuries. MTA data shows that injuries rose from 2.0 per 200,000 hours worked in January to 2.8 in September. The New York Post reports that President of MTA Capital Construction Michael Horodniceanu told a meeting of the Long Island Rail Road three days before O’Brien’s death, “We are looking at it very carefully.”